Method and Apparatus for Controlling Light Levels to Save Energy

ABSTRACT

An occupancy sensor with integral light level sensors is configured to turn off or disable peripheral circuits and go into a periodic deep sleep mode to reduce phantom loading. Peripheral circuits include occupancy sensor circuits and relay drive circuits, but may include other circuits such as communication circuits. The sensor may be configured to periodically wake itself up, check ambient light conditions to see if lighting is below the set threshold. If it is not, the sensor goes back to sleep. If it is, then the sensor can power up the occupancy sensor circuit to see if the space is occupied; if not, it can go back to sleep. If the space is occupied, it can turn on other peripheral circuits necessary to control the load.

RELATED APPLICATIONS

This application is a continuation of copending U.S. Utility Patentapplication 14/011,641 filed Aug. 27, 2013, now U.S. Pat. 9,144,139which claims priority from U.S. Provisional patent application61/693,714 filed Aug. 27, 2012.

FIELD OF THE INVENTIONS

The inventions described below relate to the field of

BACKGROUND OF THE INVENTIONS

Lighting control devices must consume a certain amount of electricalpower in order to perform their functions, such as occupancy sensing andsupplying power to lighting loads. Often referred to as “phantom loads”or “vampire loads”, this lighting control device power consumption canbe considerable in large buildings. For example, if two thousandoccupancy sensors can save 20 milliamperes of electrical current at 24volts (direct current), or 0.48 W each, then 960 W (0.96 kW) can besaved. Given inefficiencies in low voltage power supply design, thesavings at the mains power supply will be higher (10-20% higher).Multiplied over thousands of buildings in a geographic area, powersavings can be substantial.

Lighting control devices such as occupancy sensors often include anambient light level sensor that measures the amount of ambient light. Itis common for the ambient light level sensor to monitor the ambientlight level to determine if an adequate amount of light is available inthe space so that it does not need to turn lights on if occupancy isdetected. Light may come from a window or skylight or from otherelectric lights not controlled by a particular lighting control device.Typically, the ambient light level sensor allows the user to adjust theambient light level threshold at which this determination is made.

SUMMARY

The devices and methods described below provide for lighting controlcomponents such as occupancy sensors with integral light level sensors.An occupancy sensor is configured to turn off or disable peripheralcircuits and go into a periodic deep sleep mode to reduce phantomloading. Peripheral circuits include occupancy sensor circuits and relaydrive circuits, but may include other circuits such as communicationcircuits (radiofrequency or infrared). The sensor may be configured toperiodically wake itself up, check ambient light conditions to see iflighting is below the set threshold. If the ambient light conditions arenot below the set threshold, the sensor goes back to sleep. If theambient light conditions are below the set threshold, then the sensorcan power up the occupancy sensor circuit to determine if the space isoccupied; if the space is not occupied, the sensor can go back to sleep.If the space is occupied, the occupancy sensor can turn on otherperipheral circuits necessary to control the load, e.g., activate arelay or triac control circuit to supply power to the light load.Multiple levels of implementation based on stand-alone control or systemlevel control in a lighting control installation may be used.

In a stand alone installation, it is common to have an occupancy sensorthat includes an internal relay or dimming circuit (e.g., triac as isknown in the art) for controlling mains power to a lighting load.Another common installation is to have a low voltage occupancy sensorsend a signal to another device, commonly called a power pack, thatitself has a relay to control power to a lighting load; thisconfiguration allows multiple occupancy sensors to be connected inparallel to control one power pack, which may supply power to all thelighting loads in a large space.

Lighting control systems are also available. Such systems allowcomponents such as occupancy sensors and wall switches to communicatewith a control that controls power to the lighting load. The control maybe built into the occupancy sensor or other component, or it may be aseparate component. Communication may happen via wires, e.g., CATSnetwork cable or power line, or wirelessly, e.g., via radio frequency orinfrared. In such systems, an ambient light sensor may be built into anoccupancy sensor or other component, or it may be a stand alonecomponent, often referred to as a daylight sensor as are known in theart. The system may reduce power usage as noted above for just thecomponent having the ambient light sensor, however, this does not takeadvantage of additional power saving available in a systemconfiguration. In a preferred embodiment, the component having theambient light sensor sends a signal to the system components (or mastercontrol if the system is so configured) to indicate that ambient lightis above or below the set threshold. This signal may be on a dedicatedwire in a cable (e.g., a simple high or low voltage) or may be via aparticular message send over a communication bus (wired or wireless).Components receiving the signal may then shut down nonessential circuitsto reduce power usage using the techniques described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a lighting control system with lightlevel energy savings as described below.

FIG. 2 is a schematic diagram of an ambient light level sensor circuit.

FIG. 3 is a schematic diagram of a portion of a lighting controllercircuit using the light sensor of FIG. 1.

FIG. 4 is a schematic diagram of a lighting level switch for thelighting control of FIG. 3.

FIG. 5 is a schematic diagram of an ultrasonic output transducer drivercircuit.

FIG. 6 is a schematic diagram of a power supply providing the power tothe driver of FIG. 5 and the ultrasonic detector of FIG. 7.

FIG. 7 is a schematic diagram of an ultrasonic detector circuit.

DETAILED DESCRIPTION OF THE INVENTIONS

FIG. 1 illustrates lighting system 10 for controlling light levels tosave energy. System components are connected together via any suitablecables that carry a communication bus and low voltage power connectionssuch as Wattstopper's Lighting Management Registered Jack (LMRJ) cablesor any other suitable network cables such as CATS network cables. A RoomController 11, such as the LMRC-102 includes internal microcontroller 12and essential and nonessential circuits is connected to mains power 13to generate low voltage power for the system and is also the controlcomponent that controls power to the lighting load 14 (on/off relaycontrol for two independent lighting loads for this model). Other systemcomponents include closed loop daylight sensor 15 (an LMLS-400), a dualtechnology occupancy sensor 16 (LMDC-100 using ultrasonic andpyroelectric infrared sensors), and a suitable light switch 17 such asan LMSW-102 two position wall switch. An ambient light threshold is setusing a button on the LMLS-400 or via a hand held remote commission tool(not shown), but may also have a default value based on lightingrecommendations or office lighting/illumination standards. When theambient light threshold is reached, sensor 15 sends a message overproprietary bus 18 to all other system components, which respond byshutting down nonessential or peripheral circuits and maintains power toessential circuits. In the system, sensor 16 may sense occupancy and sodecide that it should keep its sensor circuits active, or it may shutdown those circuits as described above. Switch 17 may put itself intodeep sleep and only wake up if one of its buttons is pressed, indicatingthat a user wants to override the low power mode and turn on a light, orperiodically wake up to see if a message is waiting (or poll othercomponents) to reactivate nonessential circuits to come back to fulloperation. In another configuration, room controller 11 can reduce thelow voltage power supplied to the other components in the system. Thecontroller typically provides 24 volts (direct current, VDC) but thiscould be reduced to 12 VDC when ambient light exceeds the set threshold.Most components operate at 3-8 VDC internally, so this changeeffectively makes them more energy efficient.

As illustrated in FIG. 1, stand alone occupancy sensor 16 can controlpower to any peripheral circuit by including a suitable electronicswitch, such as a MOSFET or other suitable component, between theinternal power supply and the circuit to be controlled. Internalmicrocontroller 19 operating with firmware controls the operation of theelectronic switch based on input it receives from any suitable sensorsuch as ambient light sensor 20, or simple cadmium sulphide sensors,photodiodes, and advanced sensors like the TAOS TSL2550 digital lightsensor. “Microcontroller” may also mean microprocessor, applicationspecific integrated circuit, field programmable gate array, or series oflogic devices that may execute firmware, state diagram or otheroperational sequence. Depending on the sensor, the input to themicrocontroller may be a single digital input, an analog-to-digitalconverter input, or a communication bus input (e.g., the so-called “ISquared C” (I2C) bus. If the ambient light is greater than a thresholdvalue, the electronic switch is made to interrupt power to theperipheral circuit. For example, a typical ultrasonic output transducermay consume 10 milliamperes and the ultrasonic receiver may consume 2-3milliamperes, both of which can be turned off. The microcontroller thenenters a deep sleep mode that is periodically interrupted via aninternal timer, as is well known in the art, so that the firmware mayexecute routines to check ambient light level and, if necessary, startto power up other peripheral circuits as needed to determine if thelight load should be turned on. The output of the light level sensoritself may be tied to an external interrupt of the microcontroller,typically with a trimming potentiometer to set the ambient light levelthreshold to take advantage of the logic high and logic low voltageinput specifications of the microcontroller input. A very low powercomparator may be designed between the ambient light sensor andmicrocontroller to provide a clean digital signal to themicrocontroller.

In a stand alone configuration where a low voltage sensor sends a signalto a power pack, the signal from the sensor is typically generated onoccupancy detection to tell the power pack to turn on power to thelighting load. The power pack may be designed such that the absence ofthis signal causes the power pack to disable internal circuits, such asa relay drive circuit, and to go into a low power sleep mode.Alternatively, the sensor signal may be just a voltage transition foroccupancy and a pulse for the ambient light condition, or a combinationthereof. The sensor signal may be used to interrupt a microcontroller inthe power pack from its sleep, or the microcontroller may periodicallywake up and poll the sensor input signal. Alternatively, additionalsignal wires may be provided between the sensor and power pack tocommunicate the need for low power operation, but that is not preferredas it adds cost for the additional wires and their installation.

In an occupancy sensor that connects to mains voltage, an electronicswitch may be configured to be controlled directly by a passive ambientlight sensor to interrupt power to the main switching power supply thatconverts mains AC voltage into a suitable DC voltage for themicrocontroller and other electronics. The phantom load is then reducedto the power consumed by the passive light sensor and electronic switchcircuit that can be easily designed to consume microwatts of power. Theambient light sensor generates a voltage across it that is used to drivethe gate of a MOSFET designed to withstand the mains voltage, and asimple trimming potentiometer may be used to set the threshold level.When the MOSFET is placed between the mains connection and the bridgerectifier of the switching power supply, virtually all phantom power maybe eliminated. Electronic switches may also be used to control theswitching power supply, for example, by switching in different valuecomponents to reduce the current limit when there is sufficient ambientlight; this may be under direct control of the passive ambient lightsensor or the microcontroller. For example, the TNY274-280TinySwitch®-III Family (Power Integrations, Inc.) allows adjustment ofthe lower current limit that improves efficiency.

A stand alone occupancy sensor can disable portions of a sensor circuitby using a suitable electronic switch, such as a transistor. FIG. 2shows an ambient light level sensor circuit 21. LD1 and LD2 areparallel, reverse biased green LEDs that develop a voltage across themwhen exposed to light (only one is used in actual manufacture in thisembodiment, the other is at a different location on a printed circuitboard for use in a different model of product having the light sensor ina physically different location). This voltage is subsequently amplifiedand filtered by circuits based on U3 and U6D as well as passivefiltering by C58, R85, R37, C56, and C57. The output of this circuitgoes directly to an analog-to-digital converter input of microcontrollerU4 in FIG. 3. The desired ambient light threshold is set by the userusing PB1 input switch shown in FIG. 4 and whose output also goesdirectly to microcontroller U4 in FIG. 3. In a set up mode, which may beset by a series of DIP switches not shown, for example, the user pressesPB1 when the ambient light level is acceptable and the lighting load isoff to set the ambient light threshold. If the ambient light is at orabove the threshold, then the lighting load is not turned on and powersaving methods can be instituted.

FIG. 5 shows an ultrasonic output transducer driver circuit. X1 is a 40kHz crystal that is input into ultrasonic transducer TX driver circuitcomprised of U7A-E. Q7 is a transistor that is controlled by an outputfrom microcontroller U4 (FIG. 3). Crystal X1 is free running causingtransducer driver U7 to provide about 10 milliamperes of current totransducer TX to create an ultrasonic sound output. When themicrocontroller determines that the ambient light level is at or abovethreshold (or just above threshold), then it activates Q7, which causesthe crystal signal from X1 to short to ground. Transducer driver U7sends no current to transducer Tx, saving 10 milliamperes of phantomload current.

FIG. 6 shows a variable output power supply that generates the supplyvoltage V_VAR for the ultrasonic driver circuit in FIG. 5. One skilledin the art can insert a microcontroller controlled transistor betweensignal points V_VAR and TP34 to completely turn off power to theultrasonic driver circuit as well as to the ultrasonic detector circuitof FIG. 7. Although not critical to the invention, ultrasonic detectorcircuit works as follows: ultrasonic sound is picked up by receivingtransducer RX whose signal is then amplified and filtered in stagesbased on amplifiers USA, U6B and U6C. The amplified and filteredultrasonic signal at TP25 is fed to an analog to digital converter inputof microcontroller U4 (FIG. 2). The microcontroller firmware analyzesthis signal for signs of occupancy in the monitored space.

A variable output power supply can also reduce the power to theultrasonic driver circuit to achieve lower power but also maintain somelevel of occupancy sensing. When there is sufficient ambient light, thevariable power supply can be set to a lower operating voltage. Thisresults in a lower amplitude ultrasonic signal and effectively reducessensitivity. Reduced sensitivity would require a large motion to bedetected (e.g., a body coming within a certain distance of the sensor).Upon detection, the variable power supply can increase the operatingvoltage to create a stronger ultrasonic signal that is then able todifferentiate fine motion, such as hand motion at a desk, to maintainoccupancy. This can be implemented for the ultrasonic detector as well,and applies to any occupancy sensor that is driven by a certain voltagelevel (e.g., pyroelectric sensors, microwave sensors, sound sensors,etc.)

Alternatively, power to the lighting management sensor control systemsmay be controlled as a function of time. For example, all sensorcircuits are fully operational from 7:30 am to 6:00 pm on Monday throughSaturday (business hours). Between 6:00 pm and 7:30 am and on Sundays,all sensor power is off. The on and off times may be controlled by theusers and adjusted as necessary. The time control of phantom loads mayalso be a layer of power control and operate in conjunction with anoccupancy/lighting level sensor layer that only controls sensor powerlevels during business hours.

While the preferred embodiments of the devices and methods have beendescribed in reference to the environment in which they were developed,they are merely illustrative of the principles of the inventions. Theelements of the various embodiments may be incorporated into each of theother species to obtain the benefits of those elements in combinationwith such other species, and the various beneficial features may beemployed in embodiments alone or in combination with each other. Otherembodiments and configurations may be devised without departing from thespirit of the inventions and the scope of the appended claims.

I claim:
 1. A lighting control system comprising: a lighting controlcomponent with an internal microprocessor and essential andnon-essential circuits for controlling the application of mains power toloads; one or more loads operatively connected to the lighting controlcomponent; a light sensor operatively connected to the lighting controlcomponent, the light sensor producing a first signal when it senseslight levels above a predetermined threshold and a second signal when itsenses light levels below the predetermined threshold; wherein theinternal microprocessor reduces power to essential circuits when thefirst signal is received and restores full power to essential circuitswhen the second signal is received.
 2. The lighting control system ofclaim 1 wherein the internal microprocessor also disables power tononessential circuits when the first signal is received and enablespower to the nonessential circuits when the second signal is received.3. The lighting control system of claim 1 further comprising: one ormore lighting or load control sensors, each sensor having essential andnonessential circuits; a low voltage power and communication networkinterconnecting the lighting control component and the one or morelighting or load control sensors; and wherein the internalmicroprocessor transmits signals through the low voltage power andcommunication network to the one or more lighting or load controlsensors to reduce power to essential circuits when the first signal isreceived and restore full power to essential circuits when the secondsignal is received.
 4. The lighting control system of claim 3 whereinthe internal microprocessor transmits signals through the low voltagepower and communication network to the one or more lighting or loadcontrol sensors to also disable power to nonessential circuits when thefirst signal is received and enables power to the nonessential circuitswhen the second signal is received.
 5. The lighting control system ofclaim 1 wherein the light sensor is wirelessly connected to the lightingcontrol component.
 6. The lighting control system of claim 3 wherein theone or more lighting or load control sensors are wirelessly connected tothe lighting control component.